The Department of Chemical and Biomolecular Engineering welcomes Dr. Connie B. Roth, an Associate Professor in the Department of Physics at Emory University. Dr. Roth’s seminar titled, “Local Property Changes Near Interfaces in Nanostructured Polymer Blends and Films” will be held in 100 Earle Hall on October 3rd from 2:00 to 3:00 pm.
Nanostructured morphologies with extensive interfaces have become the hallmark of high performance multicomponent materials. Understanding how local material properties change near interfaces is clearly crucial to designing an optimized morphology to create the correct global macroscopic characteristics desired from an amalgam of these local effects. Contrary to the traditional textbook paradigm, our group has recently demonstrated that local dynamical properties across polymer domains can become strongly coupled upon welding of two dissimilar polymer interfaces creating broad gradients in local material properties. Using a localized fluorescence technique, we have investigated how the local glass transition temperature Tg(z) changes across interfaces between two polymers with widely different bulk glass transition temperatures Tgbulk. Starting with a single interface between two semi-infinite domains (ΔTgbulk ≈ 80 K), we show that broad profiles in local Tg(z) across dissimilar polymer-polymer interfaces are established, spanning hundreds of nanometers and observed to be asymmetric relative to the composition profile. A key finding of these results is the observation that the broad coupling of dynamics across the dissimilar polymer-polymer interface only occurs if this interface is welded together by annealing to equilibrium. Efforts to understand what factors during polymer interface formation cause these broad profiles in local Tg(z) find that chain connectivity appears to be surprisingly important. This is confirmed by measurements near silica substrates with tethered chains where low grafting densities (~10 vol% tethered chains) are observed to cause large +50 K increases in local Tg. We now explore what property changes take place in multilayer systems during interface annealing using different experimental techniques with the goal of understanding how interfaces mediate dynamical coupling across dissimilar polymer domains.
Connie B. Roth, an Associate Professor of Physics at Emory University, received her Ph.D. and M.Sc. in Physics from the University of Guelph, Canada. Following postdoctoral positions at Simon Frazier University, Vancouver, and Northwestern University, Chicago, Dr. Roth joined Emory’s faculty in 2007. Prof. Roth has received a NSF CAREER Award, ACS PRF Doctoral New Investigator grant, was the 2009 recipient of the Division of Polymer Physics (DPOLY) UKPPG Polymer Lecture Exchange from the American Physical Society (APS), and most recently received the 2019 Fellow Award from the North American Thermal Analysis Society. She is serving as the DPOLY Program Chair for the 2020 APS meeting.